1. Field of the Invention
This invention relates to a magnetic tape cartridge comprising a cartridge casing and a single reel which is housed in the cartridge casing for rotation and around which a magnetic tape is wound, and more particularly to a structure for locating in place such a magnetic tape cartridge.
2. Description of the Related Art
As a recording medium for use in an external memory of a computer or the like, there has been known a magnetic tape cartridge comprising a magnetic tape wound around a single reel and a cartridge casing in which the reel is housed for rotation. Since the magnetic tape is used for storing data in a computer or the like and important information is stored on the magnetic tape, the magnetic tape cartridge is structured so that trouble such as tape jam does not occur and the magnetic tape is not accidentally drawn out.
Further, it is necessary to accurately locate in place the magnetic tape cartridge with respect to a recording and reproducing apparatus when it is loaded in the recording and reproducing apparatus. For example, a locator portion is formed on a side surface of the cartridge casing, and the magnetic tape cartridge is located in place with respect to the recording and reproducing apparatus by a locator member of the recording and reproducing apparatus being brought into abutment against the locator portion of the cartridge casing. Further, a reference surface is formed on the bottom surface of the cartridge casing and a locator member of a recording and reproducing apparatus is brought into abutment against the reference surface when the magnetic tape cartridge is loaded in the recording and reproducing apparatus, whereby the magnetic tape cartridge is held in a predetermined level with respect to the recording and reproducing apparatus so that the magnetic tape is fed from the magnetic tape cartridge to the recording and reproducing apparatus at a predetermined level.
The cartridge casing is generally formed of upper and lower casing halves fixed together. Since the upper and lower casing halves are formed by plastic molding, the side wall surface of the cartridge casing is provided with a draft angle for facilitating ejection of the product from the mold. Further, the surface of the cartridge casing is sometimes grained to make the surface matte so that an uneven pattern generated on the surface by molding becomes less remarkable. The lower casing half is substantially rectangular in shape and comprises a bottom wall and a side wall erected from the peripheral edge of the bottom wall. Inside the lower casing half, an arcuate inner rib is formed to extend along the reel, boss portions for screwing the upper and lower casing halves are formed, and a sliding portion on which a sliding door for closing and opening a tape draw-out opening slides, a write-protector receiving portion and the like are provided. Further, ribs and steps are formed on the bottom wall of the lower casing half.
In such a cartridge casing, there has been a problem that, since a draft angle is provided to the side wall surface in order to facilitate mold release of the product and the abutment surface of the locator portion is provided with the same draft angle, the position in which the locator member abuts against the locator portion varies according to the draft angle when the position of the magnetic tape cartridge relative to the recording and reproducing apparatus fluctuates in the vertical direction, whereby the position of the magnetic tape cartridge as located by the locating member fluctuates.
Further, when a sinkmark is generated on the reference surface on the bottom surface of the cartridge casing, there arises fear that flatness and surface accuracy of the reference surface deteriorate and accuracy in locating the magnetic tape cartridge with respect to the recording and reproducing apparatus deteriorates.
In view of the foregoing observations and description, the primary object of the present invention is to provide a magnetic tape cartridge which can improve accuracy in locating the magnetic tape cartridge by the locator portion on the side wall surface of the cartridge casing and by the reference surface on the bottom surface of the cartridge casing.
In accordance with a first aspect of the present invention, there is provided a magnetic tape cartridge comprising a magnetic tape wound around a single reel and a cartridge casing in which the reel is housed for rotation, the cartridge casing being provided on a side surface thereof with a locator portion having an abutment surface which is adapted to abut against a locator member of a recording and reproducing apparatus to locate the magnetic tape cartridge in place with respect to the recording and reproducing apparatus, wherein the improvement comprises that
the abutment surface of the locator portion is provided with a draft angle for facilitating ejection of the cartridge casing from a mold smaller than the draft angle for the other part of the side surface of the cartridge casing.
It is preferred that the abutment surface of the locator portion be low in surface roughness from the viewpoint of facilitating mold release.
In accordance with a second aspect of the present invention, there is provided a magnetic tape cartridge comprising a magnetic tape wound around a single reel and a cartridge casing in which the reel is housed for rotation, the cartridge casing being provided on its bottom surface with a reference surface which is adapted to abut against a locator member of a recording and reproducing apparatus to locate the magnetic tape cartridge in place with respect to the recording and reproducing apparatus, wherein the improvement comprises that
the bottom wall of the cartridge casing is uniform in thickness and free from a rib or a step at the part where the reference surface is provided.
When the bottom wall of the cartridge casing is small in thickness, sinkmarks are less apt to be generated.
In the magnetic tape cartridge in accordance with the first aspect of the present invention, since the draft angle of the abutment surface of the locator portion is smaller than the draft angle for the other part of the side surface of the cartridge casing, the position in which the locator member abuts against the abutment surface does not largely vary even if the position of the magnetic tape cartridge relative to the recording and reproducing apparatus fluctuates in the vertical direction, whereby the position of the magnetic tape cartridge as located by the locating member can be stabilized, and the position and attitude of the magnetic tape cartridge in the recording and reproducing apparatus can be held proper.
When the abutment surface of the locator portion is low in surface roughness (e.g., a gloss surface or a surface having fine roughness), the cartridge casing can be easily ejected from the mold even if the draft angle of the abutment surface is small and generation of defective moldings upon ejection of the products can be suppressed.
In the magnetic tape cartridge in accordance with the second aspect of the present invention, since the bottom wall of the cartridge casing is uniform in thickness and free from a rib or a step at the part where the reference surface is provided, the reference surface, against which the locator member of the recording and reproducing apparatus is brought into abutment to locate the magnetic tape cartridge in place with respect to the recording and reproducing apparatus, can be free from a sinkmark, whereby flatness and surface accuracy of the reference surface can be ensured and the position of the magnetic tape cartridge as located by the locating member can be stabilized to hold proper the position and attitude of the magnetic tape cartridge in the recording and reproducing apparatus.